Programmed cell death (PCD) is a tightly controlled mechanism that eliminates unnecessary or aberrant cells, maintains tissue homeostasis, and is required for the proper shaping of organs and tissues during animal development. For instance, PCD is required for the development of sexual dimorphism through the elimination of sex-specific cells or tissues that are not needed in the opposite sex. An important question is how the cell-death pathway is regulated in response to sexual identity such that apoptosis is activated only in the appropriate cells. To address this question, I propose to study programmed deaths of C. elegans sex-specific neurons, HSNs and CEMs. We have screened for and isolated several rsd (regulator of sex-specific deaths) mutants in which the life vs. death decisions of sex-specific neurons are altered. I plan to carry out thorough genetic, molecular, and biochemical analyses of sexually dimorphic cell death in HSNs and CEMs using two interesting rsd mutants. Given that the cell-death pathway is highly conserved, this research has the potential to provide insight into how cell death is regulated in humans. Such insight may prove beneficial to clinical research on diseases that are caused by inappropriate cell death regulation such as cancer. [unreadable] [unreadable]